Large-area split type flexible magnetic tactile sensor with sensing function

Abstract

The invention provides a large-area split type flexible magnetic tactile sensor with a sensing function, and the sensor employs a plurality of flexible square magnetic sheets which are magnetized in the thickness direction, and the polarities of the flexible square magnetic sheets are alternately arranged in a checkerboard array mode in which the polarities of the magnetic fields of the adjacent flexible square magnetic sheets are opposite, so as to simulate a flexible magnetic film which is magnetized in a folded manner. The magnetic flux density of a contact force acquisition area is enhanced, a U-net algorithm is adopted to carry out field intensity-force relation fitting on the divided acquisition area, and a contact force cloud picture is generated, so that a Hall sensor and a flexible magnetic film can keep a large distance to carry out split type large-area contact force sensing, and lossless split type installation is realized; and compared with simple magnetic field modes such as unidirectional magnetization, the touch sensor has higher sensitivity. According to the size of a required contact force measuring surface, more flexible magnetic touch sensor arrays are arranged, a contact force cloud picture is drawn together through a plurality of units, and the flexible magnetic touch sensor array has application potential in the fields of bionic robots, flexible electronics, medical treatment and the like.

Description

Technical Field

[0001] The present invention belongs to the field of flexible tactile sensors, and in particular relates to a large-area split magnetic tactile sensor array with sensing function and a preparation method thereof. Background Art

[0002] Flexible pressure sensors have the advantages of good flexibility, small size, light weight and easy use. They can be widely used in electronic skin, wearable devices, smart homes, robots and human-computer interaction equipment.

[0003] Current flexible tactile sensors include piezoelectric, piezoresistive, capacitive, optical and other principles. These sensors have relatively high advantages in terms of high precision and fast response. However, as the pressure measurement area increases, the complexity of the internal circuits of these sensors continues to increase, greatly increasing the difficulty of manufacturing the sensors. At the same time, due to the mechanical contact of the sensor during use, the internal structure and circuit are easily damaged. Usually, damage to one location will cause the entire sensor to be impaired in accuracy or even scrapped.

[0004] Flexible tactile sensors based on magnetic fields have the advantages of simple structure, low cost, and the ability to produce large-area sensors, which can effectively make up for the above problems. When the magnetic tactile sensor detects contact force, it converts the change in the magnetic field when it is subjected to contact force into the size and position of the contact force. In some existing solutions, since the magnetic field generated by soft magnetic energy is small, hard permanent magnets are embedded to increase the magnetic field strength, but this leads to a decrease in flexibility and is easily damaged when the external contact force is large. Other solutions use flexible magnetic materials, but their magnetic field strength is weak, the sensing range is small, and the wireless propagation characteristics of the magnetic field are not fully utilized. The magnetic tactile sensors and the magnetic field arrays used in these solutions are mostly of fixed size, and the detection area cannot be further expanded after production is completed.

[0005] In addition, most of the existing flexible sensors are only single sensing units, which can only measure point contact force and cannot identify contact force within a range. In many application scenarios, multi-point contact force reading can only be achieved by combining and arranging multiple sensing units, which brings certain limitations to many applications in fields such as large-area sensing. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a large-area split flexible magnetic tactile sensor with sensing function and a preparation method. The sensor can be flexibly arranged through split installation, and the sensor can be expanded by simple splicing according to the current detection area. The magnetic field strength advantage of the folded magnetized magnetic film is fully utilized, and combined with the constructed "field strength-force" decoupling model, the pressure cloud map can be calculated and drawn according to the magnetic field changes generated by the plantar pressure.

[0007] A split flexible magnetic tactile array sensor with contact force sensing function, comprising:

[0008] A flexible contact layer installed on the outside of the base, the flexible contact layer includes a silicone rubber elastic layer and a flexible magnetic film which are sequentially arranged on the outside of the base; the silicone rubber elastic layer is formed by aligning and splicing a silicone rubber A layer with a cross-sectional size of 2mm and a Shore hardness of 00-30 and a silicone rubber B layer with a cross-sectional size of 2mm and a Shore hardness of A30; the flexible magnetic film is spliced ​​by flexible square magnetic sheets with a cross-sectional size of 2mm, and the flexible magnetic film and the silicone rubber elastic layer are aligned and installed up and down; the flexible square magnetic sheets have a side length of 30mm and are arranged in a chessboard polarity alternating array according to the magnetic field polarity direction, that is, the magnetic field polarity direction of each flexible magnetic sheet is opposite to the magnetic field polarity direction of the adjacent magnetic sheets;

[0009] The Hall sensor array is installed on the inner side of the base and is composed of multiple three-dimensional Hall sensors placed in set positions. One side of the chip body of the Hall sensor array is installed on the inner side of the base, and each Hall sensor chip is arranged at the midpoint of the edge line where two flexible square magnetic sheets are connected.

[0010] The flexible magnetic film and the Hall sensor array are arranged in parallel.

[0011] In the above structure, the magnetic film and the silicone rubber elastic layer are installed in an aligned manner up and down, which means that each edge of the two is aligned up and down. The base shown is the application surface of the split flexible magnetic tactile array sensor.

[0012] The split flexible magnetic tactile array sensor of the present invention adopts a split-installed flexible contact layer and a Hall sensor array. The flexible contact layer is composed of a completely flexible silicone rubber elastic layer and a flexible magnetic film. No electronic components or circuits are embedded, and there is no direct contact with the Hall sensor array. This increases the upper limit of the contact force, simplifies the manufacturing difficulty, and has higher robustness.

[0013] The flexible contact layer of the present invention adopts a design of splicing two layers of silicone rubber with different hardness. The low-hardness silicone rubber layer A is used for subsequent identification of the deformation position, and the high-hardness silicone rubber layer B is used for subsequent identification of the pressure size at the deformation location. By referring to the material properties such as the Shore hardness of the silicone rubber, the appropriate elastic layer cross-sectional size parameters are analyzed and calculated, which conforms to the collection range of plantar pressure under normal circumstances and the size restriction conditions of the pressure sensor arranged on the equipment.

[0014] The present invention adopts a chessboard polarity alternating array mode, and the magnetic field distribution obtained by Maxwell simulation is as follows: Figure 6As shown. It can be seen that square flexible magnetic sheets are used to arrange the flexible magnetic film, and the flexible square magnetic sheets are magnetized in the thickness direction, and then arranged in a checkerboard manner, that is, the magnetic field polarity direction of each flexible square magnetic sheet is opposite to the magnetic field polarity direction of the adjacent flexible square magnetic sheets. After being spliced ​​and bonded into a flexible magnetic film through this array arrangement, the magnetic flux density in the boundary area of ​​the flexible square magnetic sheets is enhanced. When the flexible magnetic film is subjected to the contact force, it moves in a plane, so that the silicone rubber elastic layer is squeezed and / or pulled to produce deformation, and the flexible magnetic film produces a spatial position displacement relative to the Hall sensor, so that the spatial magnetic field at the location of the Hall sensor array changes. By analyzing and calculating the three-dimensional magnetic field intensity data collected by each sensor chip in the Hall sensor array, the position offset of each contact force on the flexible magnetic film can be obtained. Combined with the material properties such as the Shore hardness of the flexible contact layer, the flexible contact layer is divided into units, the magnetic field data of all cells are filled into the corresponding cells, and the matrix expansion and color mapping are performed by appropriate interpolation. The U-Net algorithm is used for data fitting to obtain a pressure cloud map, and the perception of a large range of contact forces can be realized.

[0015] The Hall sensor array of the present invention is based on the magnetic field distribution of the chessboard polarity alternating array. The three-dimensional Hall sensors are arranged in the magnetic field strength enhanced area, that is, the boundary midpoint of the flexible square magnetic sheet, so as to obtain a larger magnetic field strength variation range and thus a larger pressure variation range.

[0016] The split flexible magnetic tactile array sensor of the present invention can increase the number of flexible square magnetic sheets that participate in forming the flexible magnetic film while ensuring the magnetic field arrangement rule of the chessboard polarity alternating array, thereby expanding the size of the flexible contact layer of the sensor; while ensuring the arrangement rule of the three-dimensional Hall sensor, increase the number of three-dimensional Hall sensors that participate in forming the Hall sensor array, thereby expanding the size of the Hall sensor array. When the flexible contact layer and the Hall sensor array are expanded at the same time, the overall size of the split flexible magnetic tactile array sensor can be expanded, thereby expanding the detection range of the sensor. When the size of the manufactured split flexible magnetic tactile array sensor is not large enough to cover the entire test area, multiple manufactured split flexible magnetic tactile array sensors can be directly spliced ​​to expand the detection range of the sensor, thereby simplifying the manufacturing process and eliminating the need to remake the sensor.

[0017] Preferably, the flexible square magnetic sheet can be prepared from the following materials in weight percentage:

[0018] Dragon Skin 30A component 25wt%

[0019] Dragon Skin 30B component 25wt%

[0020] 400 mesh NdFeB permanent magnet particles 50wt%

[0021] As a further preferred method, the preparation process of the flexible square magnetic sheet magnetized in the thickness direction is as follows:

[0022] The Dragon Skin 30A component, the Dragon Skin 30B component and 400-mesh NdFeB permanent magnet particles are mixed by stirring and then pre-defoamed to obtain a mixture;

[0023] The uniformly mixed mixture is placed in a pre-designed magnetic sheet mold and then degassed in sequence, and a glass plate is placed on the mold to squeeze out the excess mixture so that the height of the mixture is consistent with the height of the mold. The glass plate and the mold are then placed together in a constant temperature box for curing, and finally a flexible square magnetic sheet of the required size is demolded;

[0024] All the flexible square magnetic sheets are placed in a strong magnetic coil for magnetization in the thickness direction to obtain the flexible square magnetic sheets.

[0025] Preferably, the adhesive of the flexible square magnetic sheet can be prepared from the following materials in weight percentage:

[0026] Dragon Skin 30A component 50wt%

[0027] Dragon Skin 30B component 50wt%

[0028] As a further preferred embodiment, the preparation process of the flexible magnetic film is:

[0029] The Dragon Skin 30A component and the Dragon Skin 30B component are mixed by stirring to obtain a mixture;

[0030] The flexible square magnetic sheets are arranged alternately in a checkerboard array with polarity, so that the magnetic field polarity direction of each flexible square magnetic sheet is opposite to the magnetic field polarity direction of the flexible square magnetic sheet adjacent to it, and adhesive is applied to the joints. After being spliced ​​into a whole, they are placed in a constant temperature box for curing to obtain the flexible magnetic film.

[0031] Preferably, the silicone rubber elastic layer can be prepared from the following materials in weight percentage:

[0032] Ecoflex 0030A component 25wt%

[0033] Ecoflex 0030B component 25wt%

[0034] Dragon Skin 30A component 25wt%

[0035] Dragon Skin 30B component 25wt%

[0036] As a further preferred embodiment, the preparation process of the silicone rubber elastic layer is:

[0037] The Ecoflex 0030A component and the Ecoflex 0030B component are stirred and mixed to obtain a mixture, which is injected into a mold and vacuum degassed, and then placed in a constant temperature box for curing to obtain the silicone rubber A layer;

[0038] The Dragon Skin 30A component and the Dragon Skin 30B component are stirred and mixed to obtain a mixture, which is injected into a mold and vacuum degassed, and then placed in a constant temperature box for curing to obtain the silicone rubber B layer;

[0039] Align the silicone rubber layer A and the silicone rubber layer B up and down, apply adhesive at the joint, splice them into a whole, and put them in a constant temperature box for curing to obtain the silicone rubber elastic layer;

[0040] Preferably, the Hall sensor array is a plurality of MLX90393 chips, and the sensor chips are arranged according to a certain arrangement scheme, including an MLX90393 chip body, a PCB board and a cable interface. The arrangement scheme is that each Hall sensor is arranged at the midpoint of the edge line where two flexible square magnetic sheets are connected.

[0041] Preferably, the large-area split flexible magnetic tactile sensor also includes a single-chip microcomputer and a host computer control system connected to the Hall sensor array, divides the magnetic field area into cells, maps the corresponding magnetic field data, interpolates the magnetic field data, and uses a U-Net algorithm to perform data fitting and contact force cloud map drawing.

[0042] The design process of the cross-sectional dimension parameters of the silicone rubber elastic layer is as follows:

[0043] The silicone rubber elastic layer is regarded as a spring. The maximum compression force and elastic coefficient of the silicone rubber elastic layer are expressed as follows:

[0044] F = kx

[0045] Where F is the maximum compression force and k is the elastic coefficient.

[0046] According to the definition of strain and the stress-strain relationship:

[0047]

[0048] Where ΔL is the change in the cross-sectional dimensions of the material, L is the original cross-sectional dimension, σ is the stress, and E is the Young's modulus.

[0049] The stress σ is defined as:

[0050]

[0051] In the formula, A is the force-bearing area.

[0052] Combining the above formula, the expression of elastic coefficient k can be derived:

[0053]

[0054] The corresponding relationship between Young's modulus and Shore hardness is:

[0055]

[0056] Where HA is the Shore hardness.

[0057] Through this method, the maximum contact force that the silicone rubber elastic layer can withstand can be obtained, and according to the required situation, the appropriate thicknesses of the silicone rubber layer A and the silicone rubber layer B are designed respectively, and finally spliced ​​into a complete silicone rubber elastic layer.

[0058] The construction process of the contact force cloud graph model is as follows:

[0059] Assume that in the xy plane, there are multiple flexible square magnetic sheets with alternating polarity arranged in a checkerboard array with a thickness of d. At this time, each flexible square magnetic sheet is regarded as a magnetic dipole. The magnetic field expression of the magnetic dipole is as follows:

[0060]

[0061] Where B(r) is the magnetic field at position r, μ 0 is the magnetic permeability of vacuum, m is the magnetic dipole moment, r is the vector from the magnetic dipole to the observation point, and ||r|| is the modulus of r.

[0062] For the solution of magnetic dipole moment m, according to its definition:

[0063]

[0064] Where H is the magnetic field strength and V is the volume of the object.

[0065] Assuming that the interior of the flexible square magnetic sheet is uniformly magnetized and the internal H is negligible, the formula for the magnetic dipole moment m is finally obtained:

[0066]

[0067] The magnetic field at each point around is calculated using the assumed magnetic dipole model. The center point of the flexible magnetic film of the checkerboard array is set as the coordinate origin. The coordinates of the observation point P are (x, y, z). For each magnet i (i≤9), the magnetic field at P is:

[0068]

[0069] The total magnetic field at P is B total (P) The vector sum is:

[0070] B total (P) = ∑B i (P)

[0071] The checkerboard array method can reduce the magnetic field leakage at the edge of the magnet, so that the magnetic flux forms a closed loop between the magnets and increases the local magnetic flux density.

[0072] Taking the edge of the flexible magnetic film as the reference, a new square area is formed by equidistantly moving 7.5 mm inward, and the area is equally divided into 5×5 cell areas. For the cell containing the sensor chip, its magnetic field data is the z-axis magnetic field data collected by the corresponding sensor chip, and the magnetic field data of other cells are filled with data gaps after interpolation.

[0073] As a further preference, the steps of the interpolation method are as follows:

[0074] The 5×5 cell area is regarded as a 5×5 matrix, and its data points are f(i,j) (i,j=1,2,3,4,5), among which the data at f(1,2),f(1,4),f(2,1),f(2,3),f(2,5),f(3,2),f(3,4),f(4,1),f(4,3),f(4,5),f(5,2),f(5,4) are the z-axis data collected by the corresponding sensor chip. At the same time, this matrix is ​​expanded to a 1000×1000 grid. The new grid points are represented as (x,y) and are still divided into 5×5 intervals. In each interval [x i ,x i+1 ]×[y i ,y i+1 ] to represent the interpolation function:

[0075]

[0076] Among them, a kl is the coefficient that needs to be determined.

[0077] For each interval [x i ,x i+1 ]×[y i ,y i+1 ], there are 16 conditions (4 function values, 8 first-order derivative values, 4 mixed second-order derivative values), so 16 coefficients a need to be determined kl : Calculate the function value f(i,j) and the first-order derivative f at each grid pointx (i,j)f y (i,j), mixed second-order derivative f xy (i,j), for each interval [x i ,x i+1 ]×[y i ,y i+1 ] Establish 16 equations to form a matrix equation, and solve it to get the coefficient a kl And construct the function S(x,y).

[0078] Taking the edge of the flexible magnetic film as the reference, a new square area is formed by equidistantly moving inward 7.5 mm, and the area is divided into 5×5 cell areas of size 15 mm×15 mm. For the cell containing the sensor chip below, its magnetic field data is the z-axis magnetic field data collected by the corresponding sensor chip. For the cell without the sensor chip below, its magnetic field data is the comprehensive result of the three-dimensional magnetic field data collected by the sensor chips contained in the adjacent cells. The calculation formula is as follows:

[0079]

[0080] In the formula, x i ,y i ,z i It indicates the three-dimensional magnetic field data collected by adjacent sensor chips, and there are sensor chips at a maximum of four adjacent positions.

[0081] Through this method, each cell will obtain a corresponding data value, and the data values ​​of all cells will form a 5×5 matrix. In order to further process these data, the upper and lower limits of the matrix are set, and the interpolation method is used to expand the size of the matrix. Finally, the color is mapped according to the data value to intuitively represent the distribution of the contact force and form a cloud map.

[0082] Through the above steps, the present invention can effectively identify and display the distribution of contact force, and provide intuitive and accurate contact force feedback to the user.

[0083] The large-area split magnetic tactile sensor of the present invention simulates folded magnetization by arranging a flexible magnetic film with a conjugate magnetic field, thereby enhancing the magnetic field strength of the flexible magnetic film at the position of each Hall sensor, and performs split perception through the Hall sensor array and the flexible magnetic film, and obtains a contact force cloud map after fitting the data. Through the above settings, the large-area split magnetic tactile sensor of the present invention can realize the calculation, perception and cloud map drawing of large-area contact force based on the three-dimensional magnetic field strength and the constructed cloud map through multiple sensor units of the Hall sensor array, and has certain application potential in multiple fields such as flexible electronics and rehabilitation robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 It is a schematic diagram of the main structure of an embodiment of the present invention;

[0085] Figure 2 It is a schematic diagram of the three-dimensional structure of an embodiment of the present invention;

[0086] Figure 3 is a schematic diagram of the three-dimensional structure of a Hall sensor array in an embodiment of the present invention;

[0087] Figure 4 Schematic diagram of a magnetizing method for a flexible square magnetic sheet in an embodiment of the present invention;

[0088] Figure 5 Schematic diagram of the magnetic field arrangement direction of the flexible square magnetic sheet of the flexible magnetic film in an embodiment of the present invention;

[0089] Figure 6 Schematic diagram of the magnetic field distribution of the chessboard polarity alternating array simulated by Maxwell;

[0090] In the figure: 1 - flexible magnetic film, 2 - silicone rubber elastic layer, 3 - base, 4 - PCB board, 5 - cable interface, 6 - MLX90393 chip, 7 - flexible square magnetic sheet. DETAILED DESCRIPTION

[0091] like Figure 1 and 2 As shown, the large-area split magnetic tactile sensor with sensing function proposed by the present invention mainly includes two parts: a flexible contact layer installed on the outside of the base and a Hall sensor array installed on the inside of the base.

[0092] The flexible contact layer is composed of a flexible magnetic film 1 and a silicone rubber elastic layer 2, wherein the flexible magnetic film 1 is composed of flexible square magnetic sheets 7, the silicone rubber elastic layer 2 and the flexible magnetic film 1 are sequentially installed on the outside of the base, and the silicone rubber A layer in the silicone rubber elastic layer 2 is in contact with the flexible magnetic film 1, the thickness of the flexible magnetic film 1 is consistent with the thickness of the silicone rubber A layer and the silicone rubber B layer in the silicone rubber elastic layer 2, and the edges of the two are aligned up and down.

[0093] like Figure 3 As shown, the Hall sensor array includes a PCB board 4, a cable interface 5 and an MLX90393 sensor chip 6. The Hall sensor array is provided with one side of the MLX90393 sensor chip 6 body mounted on the inner side of the substrate, and each MLX90393 sensor chip 6 is arranged at the midpoint of the edge line where two flexible square magnetic sheets 7 are connected.

[0094] The material ratio for preparing the flexible square magnetic sheet 7 is: 25wt% Dragon Skin 30A component, 25wt% Dragon Skin 30B component and 50wt% 400 mesh NdFeB permanent magnet particles. The above components are mixed at a speed of 1000 revolutions per minute by an electric stirrer for 5 minutes, then pressurized to 5 atmospheres by a vacuum machine and left to stand for 5 minutes, the uniformly mixed mixture is poured into a mold with a groove size of 30mm×30mm×2mm, and covered with a glass plate to squeeze out the excess mixture, and then placed in a 30℃ constant temperature box for curing for 6 hours, and finally demolded to produce multiple 30mm×30mm×2mm flexible square magnetic sheets. Align the upper and lower edges of multiple flexible square magnetic sheets and place them in a magnetizer to complete thickness magnetization.

[0095] The material ratio for preparing the adhesive is: 50 wt% of Dragon Skin 30A component and 50 wt% of Dragon Skin 30B component. The above components are mixed by an electric stirrer at a speed of 300 revolutions per minute for 2 minutes.

[0096] The flexible magnetic film 1 is formed by splicing a plurality of flexible square magnetic sheets 7, and the joints are bonded by adhesive. Figure 5 Arrange as shown.

[0097] The material ratio of the silicone rubber elastic layer 2 is: 25wt% of Ecoflex 0030A component and 25wt% of Ecoflex 0030B (silicone rubber A layer), 25wt% of Dragon Skin 30A component and 25wt% of Dragon Skin 30B component (silicone rubber B layer). The Ecoflex 0030A component and the Ecoflex 0030B component are mixed by an electric stirrer at a speed of 300 revolutions per minute for 5 minutes, and the Dragon Skin 30A component and the Dragon Skin 30B component are mixed by an electric stirrer at a speed of 300 revolutions per minute for 5 minutes. The two uniformly mixed mixtures are respectively poured into two molds with grooves of 90mm×90mm×2mm in size, and covered with a glass plate to squeeze out the excess mixture, and then placed in a 30°C constant temperature box for curing for 6 hours, and finally demolded to obtain a silicone rubber layer A and a silicone rubber layer B of 90mm×90mm×2mm. The silicone rubber layer A and the silicone rubber layer B are aligned and spliced ​​up and down using an adhesive to form a silicone rubber elastic layer 2. After the silicone rubber elastic layer 2 is demolded, the adhesive is evenly coated on the upper surface. The flexible magnetic film 2 spliced ​​with multiple flexible square magnetic sheets 7 is flatly attached to the upper surface of the silicone rubber layer A in the silicone rubber elastic layer 2, and the edges of the two are aligned through a mold. The layers are cured in a constant temperature box at 30°C for 6 hours to obtain the final flexible contact layer.

[0098] The Hall sensor array 3 is composed of a PCB board 4, a cable interface 5, and an MLX90393 sensor chip 6. The size of the PCB board 4 is 90mm×90mm×1.6mm, and the size of the MLX90393 sensor chip 6 is 3mm×3mm×2mm. Each MLX90393 chip 6 is arranged at the midpoint of the edge line of the flexible square magnetic sheet 7 connected in pairs.

[0099] Before using the Hall sensor array 3, calibrate each MLX90393 sensor chip 6:

[0100] The initial values ​​collected by each MLX90393 sensor chip 6 are known:

[0101]

[0102] By getting the offset of each MLX90393 sensor chip 6:

[0103]

[0104] Combined with the mapping matrix of each MLX90393 sensor chip 6:

[0105]

[0106] The calibrated magnetic field data can be obtained:

[0107]

[0108] In this embodiment, the base 3 used for demonstration is a 3D printed resin block with a size of 90mm×90mm×3mm. The lower surface of the silicone rubber B layer in the silicone rubber elastic layer 2 of the flexible contact layer is evenly coated with adhesive, and flatly attached to the upper surface of the base 3. The edges of the two are aligned through a mold, and cured in a 30°C constant temperature box for 6 hours. Then the Hall sensor array is placed on the lower surface of the base 3, the z-axis channel of each MLX90393 chip 6 in the Hall sensor array is opened, and the Hall sensor array is moved close to the lower surface of the base 3. At the same time, the magnetic field strength value of each MLX90393 chip 6 is measured and observed. When the absolute value of all values ​​reaches the maximum value, each MLX90393 chip 6 is arranged at the midpoint of the edge line where two flexible square magnetic sheets 7 are connected. After determining the position, the adhesive is evenly applied and the Hall sensor array is attached to the lower surface of the base 3. The distance between the flexible magnetic film 1 and the MLX90393 chip 6 of the Hall sensor array is 8.6mm.

[0109] The construction process of the contact force cloud graph model is as follows:

[0110] Taking the edge of the flexible magnetic film as the reference, a new square area is formed by equidistantly moving inward 7.5 mm, and the area is divided into 5×5 cell areas of size 15 mm×15 mm. For the cell containing the sensor chip below, its magnetic field data is the z-axis magnetic field data collected by the corresponding sensor chip. For the cell without the sensor chip below, its magnetic field data is the comprehensive result of the three-dimensional magnetic field data collected by the sensor chips contained in the adjacent cells. The calculation formula is as follows:

[0111]

[0112] In the formula, x i ,y i ,z i It indicates the three-dimensional magnetic field data collected by adjacent sensor chips, and there are sensor chips at a maximum of four adjacent positions.

[0113] Through this method, each cell will get a corresponding data value, and the data values ​​of all cells will form a 5×5 matrix. In order to further process these data, the upper and lower limits of the matrix are set, and the interpolation method is used to expand the size of the matrix. Finally, the color is mapped according to the data value to intuitively represent the distribution of the contact force.

[0114] Interpolate for other cell ranges:

[0115] The 5×5 cell area is regarded as a 5×5 matrix, and its data points are f(i,j) (i,j=1,2,3,4,5), among which the data at f(1,2),f(1,4),f(2,1),f(2,3),f(2,5),f(3,2),f(3,4),f(4,1),f(4,3),f(4,5),f(5,2),f(5,4) are the z-axis data collected by the corresponding sensor chip. At the same time, this matrix is ​​expanded to a 1000×1000 grid. The new grid points are represented as (x,y) and are still divided into 5×5 intervals. In each interval [x i ,x i+1 ]×[y i ,y i+1 ] to represent the interpolation function:

[0116]

[0117] Among them, a kl is the coefficient that needs to be determined.

[0118] For each interval [x i ,x i+1 ]×[y i ,y i+1], there are 16 conditions (4 function values, 8 first-order derivative values, 4 mixed second-order derivative values), so 16 coefficients a need to be determined kl : Calculate the function value f(i,j) and the first-order derivative f at each grid point x (i,j)f y (i,j), mixed second-order derivative f xy (i,j), for each interval [x i ,x i+1 ]×[y i ,y i+1 ] Establish 16 equations to form a matrix equation, and solve it to get the coefficient a kl And construct the function S(x,y).

[0119] The matrix is ​​then further expanded to a 200×200 matrix to improve the resolution and detail of the data, and the data is color mapped, with the maximum and minimum values ​​in the data serving as the boundaries of the color mapping.

Claims

1. A large-area split flexible magnetic tactile sensor with sensing function, characterized in that: include: The large-area split flexible magnetic tactile sensor comprises a flexible contact layer, a base, and a Hall sensor array: wherein, The base is made of resin hard material; The flexible contact layer includes a silicone rubber elastic layer and a flexible magnetic film; The silicone rubber elastic layer is arranged on the outer side of the base, the side length of the silicone rubber elastic layer is consistent with the side length of the base, and the edges are aligned up and down and installed; The flexible magnetic film is arranged on the outside of the silicone rubber elastic layer, and includes a plurality of flexible square magnetic sheets; the side length of the flexible square magnetic sheets is one third of the side length of the silicone rubber elastic layer, and the sheets are arranged in a 3×3 array, and are spliced ​​into a flexible magnetic film by an adhesive, and the flexible magnetic film is aligned with the edge of the silicone rubber elastic layer and installed up and down; The Hall sensor array is arranged on the inner side of the base, the side length of the Hall sensor array is consistent with the side length of the base, and the edges are aligned up and down; The data acquisition component includes an IIC multiplexing chip PCB board, a lower computer and an upper computer. The IIC multiplexing chip PCB board is connected to the Hall sensor array. The three-dimensional Hall sensor is assigned an address through the IIC multiplexing chip PCB board, and the data collected by the Hall sensor array is input into the lower computer control system.

2. The large-area split flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: The magnetic field distribution of the flexible magnetic film is arranged in such a way that the edges of a plurality of flexible square magnetic sheets are aligned vertically and magnetized in the thickness direction so that the magnetic field polarity direction and magnetic flux density of all the flexible square magnetic sheets are consistent; when splicing, the magnetic field polarity direction of each flexible square magnetic sheet is ensured to be opposite to that of the adjacent flexible square magnetic sheets, that is, a checkerboard polarity alternating array is adopted; and adhesive is applied to the joints of all the flexible square magnetic sheets, which become a flexible magnetic film after curing.

3. The large-area split flexible magnetic tactile sensor with sensing function according to claim 1 is characterized in that The thickness of the silicone rubber elastic layer is 4 mm, and the thickness of the flexible magnetic film is 2 mm.

4. The large-area split flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: The silicone rubber elastic layer is composed of a silicone rubber layer A and a silicone rubber layer B with different hardnesses. The silicone rubber layer A is softer than the silicone rubber layer B. The low-hardness silicone rubber layer A is used to identify the deformation position, and the high-hardness silicone rubber layer B is used to identify the contact force of the deformation position. The silicone rubber layer A serves as a layer in contact with the flexible magnetic film. The two silicone rubber layers are aligned and spliced ​​up and down in the thickness direction, and are coated with an adhesive to form a silicone rubber elastic layer after curing.

5. The large-area split flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: The arrangement of the sensor chips of the Hall sensor array is as follows: according to the magnetic field distribution of the chessboard polarity alternating array, three-dimensional Hall sensors are arranged in the area where the magnetic field strength is enhanced, that is, the midpoint of the boundary of the flexible square magnetic sheet. The center point of each sensor chip is located at the midpoint of the edge line where the flexible square magnetic sheets are spliced ​​in pairs, and a total of 12 sensor chips are arranged.

6. The large-area split flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: When a larger contact force sensing range is needed, select the magnetic field distribution of the current edge flexible square magnetic piece and, while ensuring the regularity of the magnetic field distribution, that is, the magnetic field polarity direction of each flexible square magnetic piece is opposite to that of the adjacent flexible square magnetic piece, splice multiple sensors to achieve a larger range of contact force cloud map acquisition.

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